Energy Flows in the Ecosphere

Introduction Most energy on Earth derives from the radiant energy of the sun This radiant energy is transformed into chemical energy (energy stored in the chemical bonds of molecules) and mechanical energy (energy due the motion – kinetic energy - or position of an object – potential energy) It is important to understand how energy links species, and flows through ecosystems because changing the energy available at one part of the food chain causes changes throughout the ecosystem

Energy Energy is the capacity to do work and is measured in calories A calorie is the amount of heat needed to raise one gram (one millilitre) of water one degree Celsius (C), starting at 15 degrees Potential energy is stored energy that is available for later use (e.g., gasoline) Energy derived from an object’s motion and mass is known as kinetic energy (e.g., engine using gas)

Energy Most of the energy available for use is called low-quality energy diffuse, dispersed at low temperatures, difficult to gather The total energy of all moving atoms is referred to as heat, a low-quality energy vs. temperature, a measure of average speed of molecules or atoms in a substance at a particular time High quality energy, such as coal or gasoline, is easy to use, but the energy disperses quickly Energy type should be matched to use to maximize efficiency

Energy It is important to match quality of energy supply to the task at hand – not to use high quality energy (e.g. non-renewable resources) for tasks that can be done with low quality supplies (e.g. renewable resources) All organisms require energy for growth tissue replacement, movement, and reproduction

Energy

Energy Solar cells in a remote village of Thailand High-quality energy or low-quality energy source?

Energy Laws of Thermodynamics Two laws of physics describe the way in which energy transformations take place all over the world; there are trillions of transformations per second The first law is the law of conservation of energy energy can neither be created nor destroyed; it is merely changed from one form into another The total amount of energy in the universe is constant

Energy Laws of Thermodynamics The second law of thermodynamics (law of entropy) tells us that when energy is transformed from one form into another, there is always a decrease in the quality of usable energy; some energy is ‘lost’ as lower-quality, dispersed energy to the surrounding environment, often as heat Entropy is a measure of the disorder or randomness of a system. High-quality, useful energy has low entropy Organisms must continually expend energy to maintain themselves – whenever used, some is lost creating the need for an ongoing supply Also tells us energy cannot be recycled, it flows – as it flows through a system it is constantly degraded – the more it is transformed, the more it is dispersed becoming less useful

Energy Many environmental problems are a result of increased entropy Some of the principal transformations that have to take place to achieve a sustainable society are to view high energy consumption as undesirable to reduce energy waste to switch from the non-renewable sources of energy that now dominate (coal and oil particularly) to renewable sources

Discussion Question Using the laws of thermodynamics, explain why energy conservation is necessary to achieve a sustainable society – that is, a society that can meet human needs and address environmental problems both now and it the future